Tire width

I have BFG 255/60/15 on the back of my '69 Dart with 8" wide rims and a 4.5" off set. I did (many years ago) roll the wheel well lips. It makes it a close fit to the quarter panel but no rubbing and there's about 1" to the leaf spring. After putting in my new 418 stroker, I find that the BF Goodrich's are woefully inadequate I just ordered a set of jegs chrome wheels that look a whole lot like my Summit wheels that are on the car right now. I don't know why but I always seem to buy the item that they discontinue so I have to buy the Jegs wheels that look close. I also ordered a set of Mickey Thompson ET Street S/S Drag Radials.255/60/15. The specs are almost identical to the BFG's.